Neuromodulation treatments for chronic pain are known and are frequently used for treating patients. Most use large devices with batteries and long leads to electrically stimulate nerves inside the body. These devices require invasive implantation, which are very costly. They also require periodic battery replacement, which requires additional surgery. The large sizes of these devices and their high costs have prevented their use in a variety of applications that have demonstrated effective neurostimulation treatments. Additionally, most of these devices stimulate large areas of non-target nerves in addition to the desired nerves, which can have negative effects on the patient and reduce the efficacy of the therapy.
The therapeutic treatment of chronic or acute pain is the single most common reason patients seek medical care, accounting for approximately 50% of all physician office visits. Chronic pain in particular is often disabling with the associated economic impact estimated at over $100 billion. A large portion (25% to 50%) of the population that is over the age of 65 suffers from health problems that predispose them to pain. An even greater portion (45%-85%) of the nursing home population suffers from chronic pain.
The primary treatments for chronic pain are pharmaceutical analgesics and electrical/neurostimulation. While both of these methods provide some level of relief, they are not without their drawbacks. Pharmaceuticals can have a wide range of systemic side effects such as GI bleeding as well as interactions with other drugs, etc. Opioid analgesics can be addictive and can they be debilitating. Also, the analgesic effect provided by pharmaceuticals is relatively transient making them cost prohibitive, particularly for the aging population.
Neurolysis is a technique that is growing in popularity whereby a particular nerve is temporarily damaged so that it can no longer transmit pain. One method gaining in popularity is the use of neurotoxins such as botulinum toxin which must be used in large volumes on a regular basis and has a number of risks, side effects, and contraindications associated with its use. Additionally, neurolysis is primarily used to treat chronic pain, but may also have applications in acute pain under certain conditions such as those where a nerve block (such as an epidural) would be used.
Another method is the use of thermal injury from an energy source such as radio frequency or cryoablation. The procedure is minimally invasive and can be performed under local anesthesia. It has no systemic effects and does not cause permanent damage; however, there are several aspects of the existing technology available to perform such a procedure that could be improved upon.
Neurostimulators can be used for at least three different applications: neuromuscular stimulation, peripheral nerve stimulation, or spinal cord stimulation. The major drawback is that they must be surgically implanted resulting in an expensive procedure which has serious risks, side effects, contraindications, and ongoing maintenance or upgrades.
Nerve stimulation treatments have shown increasing promise recently, showing potential in the treatment of many chronic pain conditions such as neuromuscular stimulation, peripheral nerve stimulation, or spinal cord stimulation. Other conditions have also shown promise though are in much earlier stages, including drug-resistant hypertension, motility disorders in the intestinal system, and metabolic disorders arising from diabetes and obesity. The primary drawback is that they must be surgically implanted resulting in an expensive procedure which has serious risks, side effects, contraindications, and ongoing maintenance or upgrades. These treatments also have difficulty in targeting and attaching to the specific nerves for the therapy as well as delivering the appropriate energy to these nerves. Minimally invasive methods can reduce cost and risk, and improve performance by selectively modulating the proper nerves. Delivering the appropriate energy is also essential, as activity can be up-regulated or down-regulated based on the parameters of stimulation. Wirelessly powered devices with communication can be desirable because they can be miniaturized and have no need for battery replacements. However, wireless devices have an even more restrictive power budget.
Implantable devices that perform various treatments such as neuromodulation treatments are known. Most use large devices with batteries and long leads to electrically stimulate nerves inside the body. These devices require invasive implantation, which are very costly. They also require periodic battery replacement, which requires additional surgery. The large sizes of these devices and their high costs have prevented their use in a variety of applications that have demonstrated effective neurostimulation treatments.
Nerve stimulation treatments have shown increasing promise recently, showing potential in the treatment of many chronic diseases including drug-resistant hypertension, motility disorders in the intestinal system, metabolic disorders arising from diabetes and obesity, and chronic pain conditions among others. Many of these treatments have not been developed effectively because of the lack of miniaturization and power efficiency, in addition to other factors. Wirelessly powered implantables with communication are desirable because they can be miniaturized and have no need for battery replacements. However, wireless implantables have an even more restrictive power budget.
There have also been several attempts at developing miniature wireless implantable, neurostimulators, including the device described in U.S. Pat. No. 5,193,539. This device receives power wirelessly, configures stimulation, and performs electrical stimulation in a needle injectable form factor. However, the systems in place for power delivery are highly sensitive to placement and alignment, and offer limited bandwidth for data communications. The receiver operates at MHz frequencies through an inductive link, requiring multiple coils and ferrite cores. More recently, new neurostimulation devices have transitioned to operation at higher frequencies, though these devices presently rely on dipole antennas and struggle with data transfer because of challenges with high-frequency operation. Furthermore, these devices provide stimulation from directly rectifying the power waveform, reducing the precision of control and introducing additional complexity and overhead in the overall system. These systems can also have limitations in the duration of pulses that can be delivered, and long pulses can be necessary to induce therapeutic effects for many applications, including gastric stimulation. These systems also may rely on instantaneously received power to stimulate excitable tissue and do not aggregate received energy for use in therapy. Additionally, these systems may not provide for a way to use larger non-dipole antennas.
The above described miniaturized neuromodulators can achieve miniaturization in part by relying on external power source to either recharge batteries or energy storage components such as capacitors, or to instantaneously power the implant. Additionally, much of the control for proper implant operation is typically located on the controller which is external to the patient body. Therefore, the external system should have several important characteristics, such as ability to wirelessly supply power to implants, communicate with implants to program their operation and receive feedback about therapy and status of the implant, interface with the user which could be a doctor who programs and monitors the therapy or actual patient. Physically, the external system should be comfortable to wear, light weight and portable, have easy and intuitive maintenance and interface. Also, the overall system should be safe and secure for the patient and compliant with a variety of regulations while being very robust and versatile to accommodate a variety of patients, conditions, uses and applications.
There is a need for apparatus form factors that are designed for simplicity of implantation as well as effective delivery to specific locations with proper electrical connectivity to tissue. Different patients and different treatments have different requirements, and there is a need to accommodate the needs of different operating conditions.